Recently, in organic devices such as liquid-crystal display devices, solar cells and electroluminescent (EL) devices, use of transparent plastic films that are thin and light and are excellent in flexibility, as substrates in place of glass substrates that are heavy and readily cracked or broken, has been investigated. Transparent plastic substrates can be readily processed into large size panels and are applicable to a roll-to-roll production system, and therefore they are more advantageous than glass substrates in point of the producibility and cost reduction.
However, transparent plastic substrates are problematic in that their gas-barrier property is inferior to the gas-barrier property of glass. In general, the constitutive materials of organic devices may be often deteriorated or transubstantiated by water or air. For example, when a substrate having a poor gas-barrier property is used as a substrate of a liquid-crystal display device, then the liquid crystal in the liquid-crystal cell may be deteriorated and the deteriorated sites may form display faults to thereby worsen the display quality of the device.
For solving the problem, the above-mentioned plastic film substrate itself may be modified to have a gas-barrier function by itself, or the device may be wholly sealed up with a transparent plastic film having a gas-barrier property. As a gas-barrier film, generally known is one produced by forming a thin film of a metal oxide on a plastic film. As a gas-barrier film for use for liquid-crystal display devices, for example, there are known a plastic film coated with silicon oxide through vapor deposition (for example, see JP-B 53-12953 (pp. 1-3)), and a plastic film coated with aluminium oxide through vapor deposition (for example, JP-A 58-217344 (pp. 1-4)). These films have a water-vapor barrier level of 1 g/m2/day or so in terms of the water-vapor permeability thereof. Recently, however, development of organic EL displays and high-definition color liquid-crystal displays that require higher barrier capabilities has been advanced, and substrates having high barrier capabilities and usable for them have become required.
To satisfy these requirements, a gas-barrier film comprising an organic layer and an inorganic layer laminated on a plastic substrate has been developed. For example, a technique of providing a gas-barrier film that is excellent in transparency and flexibility and is hardly influenced by temperature/humidity changes has been developed, for which is used a resin prepared by curing a 6-functional acrylate or methacrylate monomer in forming the organic layer of the film (see JP-A 2002-264274). Another technique has also been developed for providing a gas-barrier film of good producibility that has a smooth surface and is transparent and flexible by using a resin prepared by curing a bifunctional or more multifunctional acryloyl group in forming the organic layer of the film (see JP-A 2004-244606).